Powder metallurgy techniques, for example for aluminium and titanium forming, are well known in the art. Rapid solidification techniques, such as electron beam melting-splat quenching techniques, utrasonic gas atomization and various rotating electrode processes are commonly used. These processes are normally suitable to produce cooling rates in excess of 10.sup.3 .degree. C. per second, and in some cases nearly 10.sup.5 .degree. C. per second.
Applicants have found, however, that by using a laser beam aimed at a glancing angle radially across a rotating surface of a metal body, such as aluminum and titanium, cooling rates greatly above 10.sup.3 .degree. C. per second may be achieved. Rates of 10.sup.6 .degree. C. per second can be achieved with a forced convection cooling using an inert gas, such as helium or argon, and high rotational speed of the metal source. This technique also has the unexpected advantage of producing metal powders of very small flake or spherical particle size, a substantial portion of which are below 100 microns in size. Typically the particles will be distributed between 50 and 150 microns in size.
The process is unique, in that a very high porportion of the particles produced are below 100 microns in size, and are very closely grouped in particle size. The resulting particles are highly useful in producing composite structures, The close grouping allows fabrication of structures with reduced waste, resulting in lower component cost and efficient material utilization. Often it is not necessary to sieve or segregate the powders prior to formation into structures. The structures formed from the resulting particles have a high strength and overall performance.
Another advantage that we have found with this process is there is very little contamination during the powder making process. In particular, there is substantially no tungsten contamination, as does result with other processes. As a result, the mechanical properties of the material, particularly titanium, are improved. Moreover, as a result, applicants' process produces powders which can be used to make alloys not possible with other methods.
Applicants have found the following U.S. Patents, the disclosures of which are incorporated by reference herein:
U.S. Pat. No. 1,915,201 PA1 U.S. Pat. No. 2,997,245 PA1 U.S. Pat. No. 3,014,812 PA1 U.S. Pat. No. 3,429,295 PA1 U.S. Pat. No. 3,539,221 PA1 U.S. Pat. No. 3,594,261 PA1 U.S. Pat. No. 3,827,805 PA1 U.S. Pat. No. 3,839,012 PA1 U.S. Pat. No. 3,963,812 PA1 U.S. Pat. No. 4,113,492 PA1 U.S. Pat. No. 4,259,270 PA1 U.S. Pat. No. 4,264,421 PA1 U.S. Pat. No. 2,267,208 PA1 U.S. Pat. No. 4,276,463 PA1 U.S. Pat. No. 4,289,952